Background/Objectives: Finding single nucleotide polymorphisms (SNPs) and candidate genes that influence the expression of key traits is essential for genomic selection and helps improve the efficiency of poultry production. Here, we aimed to conduct a genome-wide association study (GWAS) for egg production traits in an F₂ resource population of chickens (Gallus gallus). Methods: The examined F₂ population was produced by crossing two divergently selected breeds with contrasting phenotypes for egg performance traits, namely Russian White (of higher egg production) and Cornish White (of lower egg production). Sampled birds (n = 142) were genotyped using the Illumina Chicken 60K SNP iSelect BeadChip. Results: In the course of the GWAS analysis, we were able to clarify significant associations with phenotypic traits of interest and economic value by using 47,432 SNPs after the genotype dataset was filtered. At the threshold p < 1.06 × 10⁻⁶, we found 23 prioritized candidate genes (PCGs) associated with egg weight at the age of 42–52 weeks (FGF14, GCK), duration of egg laying (CNTN4), egg laying cycle (SAMD12) and egg laying interval (PHF5A, AKR1B1, CALD1, ATP7B, PIK3R4, PTK2, PRKCE, FAT1, PCM1, CC2D2A, BMS1, SEMA6D, CDH13, SLIT3, ATP10B, ISCU, LRRC75A, LETM2, ANKRD24). Moreover, two SNPs were co-localized within the FGF14 gene. Conclusions: Based on our GWAS findings, the revealed SNPs and candidate genes can be used as genetic markers for egg weight and other performance characteristics in chickens to attain genetic enhancement in production and for further genomic selection.

Avian eggs are products of consumer demand, with modern methodologies for their morphometric analysis used for improving quality, productivity and marketability. Such studies open up numerous prospects for the introduction of artificial intelligence (AI) and deep learning (DL). We first consider the state of the art of DL in the poultry industry, e.g., image recognition and applications for the detection of egg cracks, egg content and freshness. We comment on how algorithms need to be properly trained and ask what information can be gleaned from egg shape. Considering the geometry of egg profiles, we revisit the Preston–Biggins egg model, the Hügelschäffer’s model, universal egg models, principles of egg universalism and “The Main Axiom”, proposing a series of postulates to evaluate the legitimacy and practical application of various mathematical models. We stress that different models have pros and cons, and using them in combination may yield more useful results than individual use. We consider the classic egg shape index alongside other alternatives, drawing conclusions about the importance of indices in the context of applying DL going forward. Examining egg weight, volume, surface area and air cell calculations, we consider how DL might be applied, e.g., for egg storage. The value of DL in egg studies is in pre-incubation egg sorting, the optimization of storage periods and incubation regimes, and the index representation of dimensional characteristics. Each index can thus be combined to provide a synergy that is on the threshold of many scientific discoveries, technological achievements and industrial successes facilitated through AI and DL.

Relevance. Identification and analysis of the reasons for reducing egg productivity is an urgent problem in quail breeding. The aim of this study is to assess the destructive processes in the somatic cells in ovarian follicles (the level of apoptosis and pycnosis) of mature quail layers of different productivity in connection with egg production and quality indicators of eggs.Methods. In experiments, the level of apoptosis and pyknosis in granulosa cells of ovarian follicles of 3–8 mm females of Estonian, Manchurian, English white, tuxedo, English black and Pharaoh breeds was evaluated. The quails were kept in individual cages in monopreed pairs with a muted 14-hour light day. The age of the females was 160–180 days. The level of pycnotic cells was assessed by the Tarkowski cytological method, apoptotic processes were analyzed by staining with fluorochromes, propidium iodide and acridine orange (10 mcg/mlPI/AO).Results. chromatin. The results of the study of chromatin destruction using PI/AO showed a high average percentage of apoptotic cells in almost all breeds except thep < 0.05). The maximum proportion of dead granulosa cells was tested in Tuxedo and English Black layers (52% and 43% respectively). At the same time, the English white breed of quails at the age of 183 days has one of the best indicators of egg production and the proportion of yolk in relation to egg weight, which indicates the possibility of prolonging the period of their use as laying hens.

The aim of the current study was to assess the female metabolic rate and test the hypothesis that there is a relationship between the egg productivity of Japanese quails from eight breeds and their morphometric, or growth, parameters. Parameters measured were body weight (B), volume (V), and surface area (S), as well as the metabolism level expressed by the ratio S/V. The collected egg performance traits were as follows: the number of eggs produced (N), the average egg weight (W), and the total egg mass (M) (i.e., N multiplied by W). To measure the S and V values, a novel technique was developed that takes into account the similarity of the quail’s body to an ellipsoid. An analysis of the relationships between productivity indicators allowed us to introduce a new index called the metabolic index, B·S/V, based on all three main growth parameters in quails. Using the values of this index, we were then able to judge indirectly the level of quails’ egg productivity. We went on to assess the N, W, and M values, not only depending on the size of the bird’s growth parameters but also according to the degree of their changes during quail growth. These changes were expressed as the slope angles of trend lines describing the growth process data. This approach produced more accurate results for predicting the egg productivity in terms of W and M.

Smart’s model (SM) describing the geometry of avian eggs is, uniquely, based on physiological characteristics of eggs formation in oviduct walls transforming a sphere to an ellipsoid, to an ovoid. The purpose of this study was to revisit and perform a more in-depth examination of SM, providing a possible improvement in terms of reducing the number of initial parameters and compliance with geometric principles fundamental for bodies of revolution. SM requires measuring five egg parameters: length ( L ), maximum breadth ( B ), displacement of the central axis to the level of maximum breadth ( w ), and two radii of the egg at a point shifted by ¼L from the pointed ( r ) and blunt ( R ) ends, respectively. A practical test for the reproduction degree of three egg shape varieties using five-parameter model confirmed its maximum accuracy compared to all others. Modifications using four parameters ( L , B , w and r or B ₀ , which is egg diameter at ½ L ) were also relatively accurate, and only slightly inferior. Using three parameters ( L , B and w ) was clearly insufficient; however, one of our three-parameter models met the requirements of the “ Main Axiom of the mathematical formula of the bird’s egg ”. In our opinion, two of Smart’s postulates, the point of applying an oviduct force to provide the appropriate egg shape and the equality of L and the length of original ellipsoid, were used as fixed initial premises, which allowed to exclude many other possible options and to derive a mathematical model. Such an assumption arose according to the theoretical studies presented herein. Nevertheless, Smart’s formula derivation based on physiology of egg formation is a pioneering approach to the development of egg-shape models.

Egg components, including weight of yolk, albumen, and eggshell, are economically important traits in poultry breeding and production, and we thus conducted a genome-wide association study (GWAS) for them. We used an F₂ resource population of hens (n = 142) in different periods of laying, obtained by crossing breeds with contrasting phenotypes, and then genotyped them using the Illumina Chicken 60K iSelect BeadChip. Significant associations were found between 33 single nucleotide polymorphisms (SNPs) and yolk weight at 18–28 weeks of age (YW1). Eighty-seven SNPs were associated with thick albumen weight at 18–28 (TAW1) and 29–42 (TAW2) weeks of age. Four SNPs were associated with eggshell weight at 18–28 weeks of age (ESW1). Fifty-three candidate genes were identified in the positions of these SNPs, and seven prioritized candidate genes (PGCs) were revealed in regions where 2–4 SNPs associated with the studied traits were localized. These were as follows: SYTL5 (YW1, TAW1), FRY (TAW1), GABRG3 (YW1, TAW1), ALDH1A3 (YW1), VCL (YW1), HYDIN (YW1), and TIMP4 (TAW1). Allelic variants at the ALDH1A3, VCL, HYDIN, FRY, and TIMP4 loci were associated with higher YW1 and TAW1. These SNPs and PGCs are potential genetic markers for characterizing egg weight parameters and their components in chicken breeding to achieve egg production improvements.